Re: T.Rex Feather Skepticism

[Michael Habib <mhabib5@jhmi.edu>]

On Wednesday, September 14, 2005, at 10:48 PM, frank bliss wrote:

> The cute tyrant looks like a good prey item for a hungry Upper 
> Cretaceous mammal to me.  Interesting that almost all domesticated 
> barnyard birds are fluffy and cute from the egg....

Most domesticated barnyard birds are largely terrestrial, precocial 
forms (and generally galliform birds, specifically).  They are 'fluffy' 
because they must be capable of thermoregulation soon after birth.  The 
reason we tend to domesticate such birds is probably several-fold, 
including:

1) They have large, light-fiber based pectoralis major muscles (good 
for short, sprinting flights), and we find this yummy.

2) They live largely on the ground (which is related to point number 
1), which makes them easier to contain and raise.

These traits happen to be somewhat correlated with precociality (though 
this is, in part, a phylogenetic effect).  Thus, these traits are 
correlated with fluffiness.  Other than the phylogenetic constraints, 
ground-living birds that are poor sustained fliers probably tend to be 
precocial, because the offspring are under pressure to leave the nest 
early, and they presumably utilize a food source available without 
flight (since the adults are poor sustained fliers).

The exceptions to much of the above are domesticated waterfowl; in that 
they are strong sustained fliers.  However, they still feed on the 
surface (water, instead of terrestrial surfaces), and they still nest 
on the ground in accessible regions (and they are considered to be 
sister taxa to galliforms, in many analyses), so it is not surprising 
that they, too are precocial.

--Mike Habib